System to load pre-heated scrap by means of baskets for electric arc furnace

ABSTRACT

System to load pre-heated scrap by means of baskets for electric arc furnace, the furnace including a movable roof (28), at least one basket (15) loaded with scrap being arranged in a lateral position near the furnace, the basket (15) being associated with a movable covering system (18), there being included at least a pipe (20) connecting the fourth hole of the furnace with the inside of the basket (15) to convey the fumes leaving the furnace (12) with the function of pre-heating the scrap, the pipe (20) being associated with the covering system (18) and able to be moved therewith, the basket (15) being associated with moving means (16a).

FIELD OF APPLICATION

This invention concerns a system to load pre-heated scrap by means ofbaskets for an electric arc furnace.

The invention is applied in the field of steel production in order toload, by means of baskets arriving from the scrap storage zone or loadeddirectly in the pre-heating position, the electric furnaces with scrap,or other prime material similar to scrap, which is pre-heated by meansof the fumes coming from the said electric furnaces.

The electric arc furnaces to which the invention is applied can be ofthe type fed by alternating or direct current.

The invention makes it possible to reduce the times needed to open theroof of the furnace in order to load the furnace, thus limiting the heatlosses from inside the furnace towards the outside environment.

Furthermore, the invention makes it possible to load the furnace withscrap which has been heated in the same moving basket used to unload thescrap into the furnace.

Moreover, the invention makes it possible to automate the movementsneeded for loading, to drastically reduce the times of the cycle, andtherefore reduce the downtimes of the furnace, and minimises the spacesrequired, both horizontally and especially vertically, in order to carryout the pre-heating and loading operations.

The invention may be used both in new installations arranged for thepurpose and also in the revamping of existing installations usingconventional-type furnaces.

STATE OF THE ART

The state of the art includes electric arc furnaces used to producesteel from scrap and regenerated material of various types.

In the state of the art, the furnaces can be loaded continuously, forexample by means of conveying means such as a belt, connected with theinside of the furnace and fed continuously with fresh scrap whichgradually replaces that already loaded into the furnace.

In another solution, the furnaces are loaded discontinuously by means ofbaskets which, in one or more steps, are loaded in a scrap-loading zoneand then transported, by lifting and moving means, for example by bridgecranes, in correspondence with the mouth of the furnace which is kepttemporally open. The bottom of the basket, which normally consists ofmovable doors, valves, teeth, sliding retaining grates or other openingsystems, is then opened and the material is unloaded inside the furnace.

Systems using baskets for loading the furnace which are known to thestate of the art have a plurality of disadvantages.

Firstly, it takes a long time to load the furnace because of thecombination of opening movements of the roof and positioning of thebaskets; this causes a considerable heat loss from inside the furnacetowards the outside, and also the leakage into the surroundingenvironment of fumes containing powders, particles and other pollutants.

A further disadvantage is that if the scrap is loaded cold into thefurnace, it takes longer to melt and causes problems for the penetrationof the electrodes.

At present, in some steel plants the furnaces are loaded with scrapwhich is pre-heated by the heat of the fumes discharged from the furnaceitself through the fourth hole on the roof.

Loading systems known to the state of the art where the scrap ispre-heated use loading baskets located in the appropriate rooms intowhich the fumes are conveyed before they are purified and discharged bythe appropriate plants.

There are also solutions known to the state of the art which include asingle room which contains several loading baskets, or several roomsconnected to each other, each one of which contains a single loadingbasket. These solutions cause problems in the structuring of the rooms,the movements of the baskets and wear on the baskets too.

Moreover, in the case of baskets heated inside the room, the scrap losespart of the heat it has accumulated, both when it is removed from theroom and when it is transported to near the mouth of the furnace andalso when it is unloaded into the furnace, from which there is alwaysand in any case a considerable heat loss. The scrap moreover is notheated uniformly from one basket to the next.

These systems furthermore are not very functional, they are veryexpensive, and they take up a great deal of space inside the plant.

Another disadvantage of this type of loading system is that it isnecessary to limit the use of the lifting cranes for the basket to thescrap-loading step, that is-to say, to the melting cycles of thefurnace; it is not therefore possible to use the cranes for otherpurposes required by the steel plant.

A further disadvantage is that the pre-heating rooms are normallylocated in positions which are not very near the furnace, and thereforethe times needed to transport the baskets from this position to thefurnace are very long and the heat losses are very high.

There are also systems known to the state of the art which load thefurnace with stable containers, which can be moved only from a heatingposition to one wherein they load the furnace, in which case thecontainers are loaded either with conveyor belts or with baskets.

U.S. Pat. No. 4,736,383 teaches to heat the scrap with the fumes leavingthe furnace and then unload the scrap into the furnace. The scrap isheated from above to below in a stationary, vertical container and thefumes also lap the lower opening means of the container.

According to this document it is necessary to displace the furnace, withall the problems of moving and positioning which that entails. If on theone hand this teaching has the advantage that the scrap is heated in adifferentiated manner from top to bottom, on the other hand it iscomplex, cumbersome, considerably difficult to manipulate, position andcenter, and has considerable problems of maintenance and management;moreover, the system involves transferring the scrap from the baskets tothe vertical stationary container, which causes problems of verticalspace.

WO 96/32616 teaches to heat the scrap in a container which is solid witha moving structure, the scrap being heated from the bottom to the top.

This document does not give the advantages of heating the scrap from thetop to the bottom; nor is it possible, with this invention, to use thebaskets directly as the scrap must be transferred to the container withthe consequent problems of vertical space. There is no possibility ofacting directly with autonomous baskets, nor is it easy to carry outmaintenance operations.

Both these systems, moreover, have the disadvantage that it is necessaryto load the stationary containers from above by means of bridge cranes,and this system takes up a considerable amount of vertical space whichmay not be compatible with the characteristics of the plant where thefurnace is to be installed.

Moreover, the loading system incorporating stationary containersinvolves great operating difficulties, safety problems, movementproblems, increases in the cycle times and a whole series of otheroperating disadvantages.

WO 95/12690 describes a movement system with a rotary tower forcontainers in which to pre-heat the scrap; the system does not usebaskets of the removable type but a substantially stationarysingle-block structure, which involves obvious limitations to theversatility, flexibility and operativity of the plant.

It is complex and difficult to move the single-block structure, and itrequires considerable civil engineering works and very high powersupplies.

This embodiment, moreover, is difficult to adapt for use in therevamping of pre-existing plants.

EP 636,698 shows a pre-heating system comprising a carousel deviceplaced in proximity of the furnace and containing three containers forthe scrap, two of which are connected in parallel to the fume outlet ofthe furnace.

This system is used for pre-heating, but the document does not explainthe methods for loading the scrap into the furnace which howeverpresumably include transfer by means of a bridge crane; the baskets arepresumably transferred from the loading position to the pre-heatingposition on the carousel by means of a bridge crane.

The baskets are also loaded, in a remote position which is differentfrom the pre-heating position, by means of a bridge crane; this impliesconsiderable vertical space occupied, which will require the adequatestructures in the plant.

Moreover, all these transfer operations seriously affect the times ofthe cycle, which are considerably lengthened for every pre-heating andloading operation.

U.S. Pat. No. 4,506,370 includes a preheating and loading device using abasket or container which can be moved on rails from the pre-heatingposition to the loading position and vice versa.

This solution does not enable more than one basket to be heated at onetime, so that the times of the cycle are consequently extended.

Moreover, the fumes which come out of the basket of scrap are notprocessed and therefore they carry with them powder and particles, aswell as unburnt aromatic compounds, which damage the filters and shortentheir working life.

There is also the document EP 287,550 which includes a rotary carouselon which three baskets are located; they pass alternately from apre-heating position to a scrap loading position after the content hasbeen unloaded into the furnace.

In this solution, however, the baskets are located under the furnace sothat, in order to unload the raw materials into the furnace, it is inany case necessary to lift them by means of a bridge crane, andtherefore in this solution too considerable vertical space is requiredin the plant.

All these systems, apart from the above-mentioned disadvantages, alsorequire the installation of specialised, stationary structures, whichrequire long preparation times and take up a great deal of space. Suchsystems cannot therefore be adopted in a short time and with relativelylimited installation costs for the revamping of existing steel works.

The present applicants have therefore designed, tested and embodied thisinvention to overcome the shortcomings of the state of the art and toobtain further advantages.

DISCLOSURE OF THE INVENTION

The purpose of the invention is to obtain a system to load pre-heatedscrap by means of baskets for electric arc furnaces, which will give aplurality of operating and management advantages in the melting cycle ofan electric arc furnace.

The term scrap includes other raw material similar to scrap.

The system according to the invention is particularly though notexclusively indicated for the revamping, in a relatively short time andwith limited costs, of existing steel works and installations withminimum modifications both on the lay-out of the plant in general and onthe furnace itself, without changing the type of functioning andparticularly the system to move and rotate the roof.

The invention can however be used also in completely new applicationsand installations.

To be more exact, the invention can avoid the need to use bridge cranesto transfer the baskets from the pre-heating position to the loadingposition and vice versa if the vertical dimensions of the plant do notpermit it, or in any case make it difficult.

Moreover, the invention can rationalise the steps of prearranging thebaskets in such a way as to obtain a considerable saving in the times ofthe cycle.

The invention can also obtain advantages in terms of eliminating thenoxious and toxic residues sent to the processing plant, thus extendingthe working life of the filters.

The invention provides to load into the furnace, by means of baskets,scrap which has been pre-heated by the fumes coming from the fourth holeof the furnace during the melting cycles.

The fumes are conveyed towards the baskets, giving up at least part oftheir heat energy to the scrap, by means of the appropriate pipes whichon the one side are connected with the fourth hole of the furnace and onthe other cooperate with the covering system of the baskets which areloaded with scrap.

According to a variant, two baskets are associated simultaneously inparallel with the pipes which convey the pre-heating fumes so that thetimes of the cycle needed to carry out the pre-heating procedure areconsiderably shortened.

According to the invention, the baskets loaded with scrap are arrangedwith rotary platform means arranged on one circumference in such a waythat at least one of the baskets is in a position of close proximitywith the furnace and substantially aligned with the furnace.

The rotary platform means have two stations, or seatings, where thebaskets are arranged, respectively a first pre-heating position wherethey are prepared for unloading and a second, waiting position.

According to a variant, the rotary platform means have at least twopre-heating and pre-unloading seatings and one or more waitingpositions; this is to allow the simultaneous pre-heating of two baskets,thus increasing the flexibility of the system and obtaining a very highenergy re-use.

Each basket is associated with respective movable moving means, forexample of the trolley type, cooperating with mating guide systems, forexample of the type including tracks or rails, or some other similarsystem, solid with the rotary platform means.

The rotary platform is arranged at such a height that the bottom of thebasket is positioned substantially on a level with the roof of thefurnace so that the baskets are moved from the pre-heating position onthe platform to the loading position above the furnace on asubstantially horizontal plane by means of the movable trolley.

There is therefore no need to lift the baskets and therefore there is noneed to use cranes, bridge cranes or similar means in order to move thebaskets.

The baskets may be autonomous, removable means with respect to thetrolley or, according to a variant, they may constitute an integralstructure therewith.

In one embodiment of the invention, the pre-heating and pre-unloadingseatings are arranged on the platform substantially on the axis of thefurnace, whereas the waiting position or positions are displacedsideways with respect to the axis of the furnace.

According to a variant, at least in their pre-heating position, thebaskets cooperate at the lower part with systems to discharge the fumeswhich remove the fumes leaving the bottom of the baskets and convey themtowards a lower chamber for collection and sedimentation.

According to a variant, the collection and sedimentation chamber isequipped with burners and also acts as a combustion chamber for theunburnt gaseous residues present in the fumes in such a way that thefumes arrive at the processing system downstream at least partlypurified and therefore less dangerous for the filters.

The sequence for loading the furnace includes, in succession, thefollowing steps.

The basket arriving from the scrap loading zone is positioned on therotary platform means in a waiting position while the loaded basket orbaskets,are already in a pre-heating position, aligned with the furnaceand ready to be unloaded.

In this pre-heating position, the baskets have their relative coveringsystem in a closed position and are connected with the pipe which isconnected to the fourth hole of the furnace which conveys the fumesleaving the furnace inside the basket.

When the first melting cycle of the furnace has finished, the roof isremoved from the furnace so as to leave the mouth free.

At this point, the system to cover the baskets, which is associated withthe pipe to convey the fumes, is also removed so as to allow the basketsto move freely.

The covering system can be moved rotatably, vertically, or bothrotatably and vertically with respect to the basket.

According to a variant, a single covering system is associated with atleast the two baskets arranged in the pre-heating and preparation forunloading position.

The basket loaded with pre-heated scrap which is nearest the furnace istranslated by means of the relative movable moving means which move on asubstantially horizontal plane, into a position above the mouth of thefurnace and unloads the pre-heated scrap inside.

The scrap is unloaded by opening the bottom of the basket by means ofvalves, gratings or similar means.

When unloading is completed, the empty basket is taken back to theoriginal pre-heating position on the rotary platform means.

At this point, the rotary platform means rotate and take the fullbasket, which was in the waiting position, to the pre-heating andpre-unloading position, whereas the empty basket is taken to a dischargeposition.

At the same time as the rotary platform rotates, the roof of the furnacecloses, thus ensuring a minimum energy loss from inside the furnace, anda new cycle to melt the scrap is begun.

The system to cover the baskets is then returned to a closed position.

The empty basket is removed from the system and transferred to the zonewhere the scrap is loaded, while a new full basket is placed in thewaiting position on the rotary platform means.

According to a variant, the empty basket in the waiting positioncooperates with a system to load the scrap which is equipped with ascrap carrier.

This solution makes it possible to considerably limit the times requiredto move the baskets, and possibly to reduce the number of baskets used.

With this embodiment, moreover, it is possible never to move the basketof the relative moving means and therefore to use integratedbasket/trolley structures.

According to a variant, at least some of the baskets used in the loadingsystem according to the invention are of the water-cooled type.

ILLUSTRATION OF THE DRAWINGS

The attached Figures are given as a non-restrictive example and showsome preferential embodiments of the invention as follows:

FIG. 1 shows a plane view of a first embodiment of the system to loadpre-heated scrap according to the invention;

FIG. 2 shows a variant of FIG. 1;

FIG. 3 shows a side view from A of FIG. 1;

FIG. 4 shows a side view from B of FIG. 2;

FIG. 5 shows a plane view of another variant of FIG. 1;

FIG. 6 shows a partial side view from C of FIG. 5.

DESCRIPTION OF THE DRAWINGS

In the following description, the reference number 10 denotes generallythe system according to the invention to load pre-heated scrap using arotary platform 11 arranged in a position of proximity to the electricarc furnace 12.

To be more exact, FIG. 1 shows an application of the system 10 incooperation with the slagging-door side of the electric arc furnace 12while FIG. 2 shows an application cooperating with the side of thefourth hole of the furnace 12.

The rotary platform 11, together with the baskets which it supports andthe systems to convey and discharge the fumes which are connected to thebaskets, constitutes an extremely compact structure, of limited bulkboth horizontal and vertical, which does not require. great works ofcivil engineering and which therefore can be easily, and relativelyrapidly, installed in association with already existing plants whichhave not been pre-arranged for the purpose.

In the applications shown, the furnace 12 is of the alternating currenttype and includes three electrodes 13 associated with respectiveelectrode-bearing arms 14.

The rotary platform 11 includes in -this case three positioningseatings, respectively 11a, 11b and 11c for the respective basketsloaded with scrap, shown respectively as 15a, 15b and 15c.

The full baskets 15a and 15b are in the respective pre-heating andpre-unloading positions 11a and 11b, while the basket 15c, also full, isin the waiting position 11c.

It is the same case when the rotary platform 11 of different size and/orstructure is able to be associated with one or three or more baskets inthe pre-heating position and with two or more baskets in the waitingposition.

In their pre-heating and pre-unloading seatings 11a and 11b, the baskets15a and 15b are arranged, in this case, substantially on the axis of thefurnace 12 and are mounted on respective trolleys, 16a and 16b, suitableto travel on a substantially horizontal plane on tracks 17 so as toperform movements towards and away from the furnace 12.

In the pre-heating and pre-unloading position, each basket 15a, 15bcooperates with a movable covering system 18 which includes an air-tightcover 19 for each of the baskets 15a, 15b.

The covering system 18 is movable and can be released from the relativebaskets 15a, 15b, for example rotatably and/or vertically, during thesteps of transferring the baskets from the pre-heating position to theposition where the scrap is unloaded into the furnace.

A pipe 20 connects the fume outlet hole, or fourth hole, of the furnace12 to the covering system 18 to convey the fumes leaving the furnace 12inside the baskets 15a, 15b in order to pre-heat the scrap containedtherein, lapping it from the top to the bottom.

According to a variant, the pipe 20 is cooled.

The fumes, after lapping the scrap contained in the baskets 15a, 15b andafter giving up at least part of their heat energy, are taken from thebottom of the baskets 15a, 15b, consisting of movable and cooled gridsor valves which allow the fumes to pass, and sent by means of respectivepipes 24a and 24b inside a collection and sedimentation chamber 21which, in this case, also acts as a post-combustion chamber.

The collection and sedimentation chamber 21 can be located eitherdirectly below the seatings 11a and 11b, with the baskets 15a, 15b inthe pre-heating and pre-unloading position, or below the seatings 11c,11d, according to the existing lay-out and the requirements ofinstallation, by providing the appropriate connection ducts.

The collection and sedimentation chamber 21 is associated with aplurality of burners 22 attached to its side walls 21a and is connectedwith at least a discharge conduit 23.

The noxious content of the fumes, for example residual CO or variousorganic compounds, is at least partly abated by the post-combustionprocess in the collection and sedimentation chamber 21; the fumes arethen sent, by means of the discharge conduit 23, to the systems offurther treatment and to the chimney.

On the conduits which connect the pipe 20 to convey the fumes with theinside of the baskets 15a, 15b and on the pipes 24a, 24b which cooperatewith the apertures to discharge the fumes in the baskets 15a, 15b, thereare respective interception means 25a, 25b at the inlet and 125a, 125bat the outlet.

Connected with the pipe 20 there is also another pipe 26, equipped withits own interception means 27, which is directly connected with thecollection and sedimentation chamber 21, in correspondence with the axisof rotation of the rotary platform 11.

In the event that the pre-heating system should be put temporarily outof use or disactivated for whatsoever reason, the interception means 25aand 25b are closed, and the interception means 27 are opened, thuscausing the baskets 15a, 15b to be by-passed, and the fumes are conveyeddirectly from the furnace 12 to the collection and sedimentation chamber21.

In this way, every operational or emergency situation can be dealt withwithout having to switch off or close down the furnace 12.

During the operational step, when the furnace 12 has finished its cycleof melting the scrap loaded during the previous step, the roof 28 isremoved and taken to a position of non-contact, shown by a line ofdashes 28a in FIGS. 1 and 2.

Additionally, the covering system 18 comprising the covers, or hoods 19which hermetically cover the tops of the baskets 15a, 15b and the cooledpipe 20, are translated by means of the relative movable trolley 29 soas to allow the full basket 15a to move freely.

The movable trolley 16a then translates the basket 15a on the relativetracks 17 until it cooperates with the mouth of the furnace 12 which ismomentarily open.

The bottom of the basket 15a is opened, in a manner known to the stateof the art, and the scrap inside the basket is unloaded into the furnace12.

When the unloading is completed, the basket 15a is taken back to itsoriginal position.

At this point, the rotary platform 11 rotates in the direction shown bythe reference number 30, in this case by 90°, and takes the basket 15b,with the relative movable trolley 16b to position 11a which waspreviously occupied by the basket 15a, and basket 15c, with the relativemovable trolley 16c, to position 11b previously occupied by basket 15b.

The covering system 18, together with the cooled pipe 20 to convey thefumes, is taken back to the operational position and thus closes at thetop and seals the full baskets 15b and 15c.

The empty basket 15a, with the relative movable trolley 16a, isdisplaced in correspondence with the seating 11d.

The empty basket 15a, in a first embodiment, can be removed from therotary platform 11, for example by means of a bridge crane if thedimensions and the structure of the plant allow, and be replaced by anew, full basket arriving from the scrap-loading zone, this new basketbeing placed in the waiting position 11c.

In this way, the cycle can proceed substantially without anyinterruption until the end of the melting cycle of the furnace 12.

According to the variant shown in FIGS. 5 and 6, which uses a rotaryplatform 11 with four baskets, the empty basket 15c, in the waitingposition 11c, is loaded by means of a conveyor belt 31 which has theoutlet end 31a cooperating with the mouth of the empty basket 15c.

The basket 15c is then filled with scrap 32 without needing to be movedfrom its position on the rotary platform 11.

When the furnace 12 has been loaded by means of the basket 15a, theempty basket 15a is taken to a waiting position lid, by the rotaryplatform 11 rotating through 90°.

The 90° rotation takes the basket 15b to the pre-heating position 11a inproximity to the furnace 12, ready for unloading into the furnace; thebasket 15c is taken to the pre-heating position 11b behind basket 15b,and basket 15d is taken to the loading position lic under the conveyorbelt 31.

According to a variant not shown here, the rotary platform 11 has threepositioning seatings and each rotation following each unloading cycleinto the furnace 12 covers an angle of 120°.

The conveyor belt 31 includes, according to a variant, a rotarydistributor element 34 which serves to regulate and make uniform thedistribution of the scrap 32 inside the basket 15, preventing thematerial from accumulating and piling up at specific points of thebasket 15.

In one embodiment of the invention, the rotary distributor element 34 isof the magnetic type.

According to a variant, the rotary distributor element 34 is of themechanical type.

The whole loading cycle of the furnace 12 including the pre-heating ofthe scrap can therefore be carried out with an extremely limited numberof baskets 15, three in this case, and with extremely limited movements.

The whole system can be automated and all the steps of the cycle can bemanaged and controlled from the command post 33.

The covering system 18, together with the cooled pipe 20, can be removedfrom the zone immediately around the furnace 12 by using the tracks 117so as to allow routine or special maintenance both on parts orcomponents of the furnace 12 and on parts or components of thepre-heating system 10.

What is claimed is:
 1. System to load pre-heated scrap by means ofbaskets into an electric arc furnace, the furnace including a roof whichis moved from a closed position to a position of non-contact, therebeing included on the roof a fourth hole to discharge fumes, at leastone basket loaded with scrap being arranged in a lateral position onrespect of the furnace, the basket being associated with a coveringsystem which is moved from a closed position to at least one position ofnon contact, there being included at least a pipe connecting the fourthhole of the furnace with the inside of the basket to convey the fumesleaving the furnace to the inside the basket as a function ofpre-heating the scrap contained in the basket, the pipe being associatedwith the covering system and being moved therewith, the bottom of thebasket being at least partly openable and associated with relativemoving means, the system being characterized in that it comprise arotary platform defining a first position, for a first basket, ofpre-heating and pre-arranging for unloading of the scrap into thefurnace and a second position, for a second basket, of waiting, thebaskets on the platform being mounted on a respective movable trolleyable to translate each basket, when the basket is in said first positiontoward a mouth of the furnace in order to unload the pre-heated scrapinto the furnace, and to move back each basket in said first positionafter the unloading of the scrap into the furnace, said unloading beingperformed by the opening of the bottom of the basket, after eachunloading cycle the baskets exchanging their respective positions bymeans of the rotation of the rotary platform, the rotary platformdefining a positioning of the baskets with the relative bottomsubstantially on a level with the mouth of the furnace, there beingincluded below the basket in the first position a chamber for thecollection and sedimentation of fumes through which the fumes pass andare possibly combusted after leaving the baskets located in the firstposition.
 2. System as in claim 1, characterized in that said rotaryplatform defines at least two pre-heating and pre-unloading positionsoccupied by respective baskets arranged on an axis with the furnace andsubjected, in parallel, simultaneously to pre-heating.
 3. System as inclaim 1, characterized in that at least in the waiting position an emptybasket cooperates with means for removing the empty basket from therotary platform.
 4. System as in claim 1, characterized in that at leastin the waiting position an empty basket cooperates with means to loadthe scrap into the empty basket.
 5. System as in claim 4, characterizedin that the means to load the scrap comprises a conveyer belt and arotary distributor element to uniformly distribute the scrap.
 6. Systemas in claim 1, characterized in that between the pipe and the coveringsystem there are respective means to intercept the fumes which aremomentarily activated.
 7. System as in claim 1, characterized in thatthe covering system is rotatably and vertically movable.
 8. System as inclaim 1, characterized in that between a lower part of each basket andthe chamber for the collection and sedimentation of the fumes there arerespective means to intercept the fumes which are momentarily activated.9. System as in claim 1, characterized in that the pipe communicatesdirectly with the chamber for the collection and sedimentation of thefumes by means of a pipe equipped with its own means to intercept thefumes which are momentarily activated.
 10. System as in claim 9,characterized in that includes means to divert the fumes directly fromthe fourth hole of the furnace into the chamber for the collection andsedimentation of the fumes through the pipe by-passing the basketlocated in the first position.
 11. System as in claim 1, characterizedin that the collection and sedimentation chamber also functions as apost-combustion chamber for the fumes.
 12. System as in claim 11,characterized in that the collection and sedimentation chamber isequipped with post-combustion burners.
 13. System as in claim 1,characterized in that at least one basket is cooled.
 14. System as inclaim 1, characterized in that the pipe to convey the fumes from thefurnace to the basket in the first position is cooled.
 15. System as inclaim 1, characterized in that the fumes flow inside the basket in thefirst position through the scrap from the top downwards.
 16. System asin claim 1, characterized in each basket includes apertures on a bottomof the basket through which to discharge the fumes.